1. Field of the Invention
The present invention relates to a radiation image detection apparatus for reading out a radiation image signal from a radiation image detection unit that detects radiation transmitted through a subject and outputting the radiation image signal as a radio communication signal. The invention also relates to a radiation image photographing system having the radiation image detection apparatus.
2. Description of the Related Art
Various types of radiation detectors that record a radiation image of a subject by receiving radiation transmitted through the subject have been proposed and put into practical use in the medical field and the like.
For example, a radiation image detector that uses a semiconductor, such as amorphous selenium or the like, that generates charges by receiving radiation is known, and a so-called optical readout type and a TFT readout type are proposed as such radiation detectors.
As a radiation image photographing system using one of such radiation detectors, Japanese Patent No. 3494683 (Patent Document 1) describes a radiation image photographing system in which radiation image signals detected by the radiation detector are transmitted to a processing unit by radio communication and signal processing, including image processing and the like, is performed in the processing unit.
Further, Japanese Unexamined Patent Publication No. 2006-263339 (Patent Document 2) proposes an electronic cassette that allows high speed radio communication capable of transferring a large volume of radiation image signals rapidly by the use of a high radio frequency.
When outputting radiation image signals as radio communication signals as in Patent Document 1 and Patent Document 2, however, if an already readout radiation image signal is outputted as a radio communication signal while reading out a radiation image signal from the radiation detector, the radiation image signal being read out from the radiation detector is influenced by the radio wave of the radio communication because the radiation image signal being read out is very weak and noise is included in the signal, resulting in degraded image quality of the radiation image.
Consequently, Japanese Unexamined Patent Publication No. 2006-247102 (Patent Document 3) discloses a method in which the operation of a communication module that outputs radio communication signals is stopped while reading out a radiation image signal from the radiation detector.
Further, Japanese Unexamined Patent Publication No. 2003-210444 (Patent Document 4) discloses a method for preventing the influence of radio communication signals on radiation image signals being read out by causing an antenna that emits radio communication signals as a radio wave to have directionality and preventing the radio wave from being emitted to the radiation detector and a detection unit that reads out radiation image signals from the radiation detector.
The method described in Patent Document 3 does not allow radio communication while reading out radiation image signals from the radiation detector, so that the processing speed is reduced. Further, unavailability of radio communication while reading out a radiation image signal from the radiation detector results in that the system is not able to deal with photographing of a preview image or a motion image which requires radiation image signal reading and radio communication to be performed in parallel.
Further, the method described in Patent Document 4 restricts the locations of antennas on the transmit side (electronic cassette) and receive side (console) for the radio communication signals, resulting in unfriendly system.
In view of the circumstances described above, it is an object of the present invention to provide a radiation image detection apparatus and radiation image photographing system capable of preventing the influence of a radio communication signal on a radiation image signal being read out without reducing the processing speed.